Heretofore the following control systems for stopping an engine are known:
(1) The engine is made to stop by cutting fuel to the combustion chamber.
(2) The engine is made to stop by cutting air to the combustion chamber.
(3) The engine is made to stop by cutting both fuel and air to the combustion chamber.
(4) The engine is made to stop by cutting air to the combustion chamber while gradually reducing fuel to the combustion chamber.
Further, in Japanese Laid-Open Patent Publication No. 2001-41072, in an automatic engine stop control, it is proposed to reduce shocks by gradually lowering engine torque.